Most Macs, if you decide not to replace them, can last beyond 8 years of use. Many schools still use the old eMacs, from 9 years ago now.
Average lifespan of a PC is 2 years. Get a $1000 PC every 2 years for 8 years, and you end up spending $4000. Spend $2000 on a MacBook Pro and keep it for 8 years, and you already save 2 grand.
It's not shelling out money. It's an investment, an investment which also has a high resale value. Very handy when you want to replace your MacBook Pro, but don't want to waste money.
Not only that, as long as Apple supports Intel processors, the software made for Macs will be guaranteed to run on your computer. As long as the operating system is supported on your Mac, it will be able to do most things that a newer Mac will be able to do.
When people say Macs are not worth the money, they only think of now. But when you buy a Mac, you think of the future, and the benefits it will have over any PC when it gets older.
Sure, PC laptops can live very long. But you will always notice slowdowns, bottlenecks, restrictions, etc. while a well-maintained Mac will not.
Also, just to let you know, smart people do not buy Macs for OS X. Smart people buy OS X for hackintoshes, or if they think a Mac is worth it, then they just buy a Mac.